The present invention relates to a station selecting device in which the tuning voltage is selectively supplied to an electronic tuner to tune in the desired station.
In the conventional device --for example, CATV in the United States--a number of variable resistors with respective fixed resistors connected to each end thereof are grouped into three bands as shown in FIG. 1, i.e., 2nd to 13th channels, A- to L-channels, and M- to W-channels. Each variable resistor produces a tuning voltage that corresponds to a certain channel. Assigned to the 2nd to 13th channels are variable resistors 7a . . . 7n with resistors 1a . . . 1n and 2a . . . 2n connected to respective ends. For A- to L-channels are used a group of variable resistors 8a . . . 8n having resistors 3a . . . 3n and 4a . . . 4n connected to their respective ends. For M- to W-channels, variable resistors 9a . . . 9n with resistors 5a . . . 5n and 6a . . . 6n connected at their ends are used. The resistors of each band are connected in parallel with each other. The resistors 1a . . . 1n, 3a . . . 3n and 5a . . . 5n are connected at one end to the terminal 15 which in turn is connected to the power source. The resistors 2a . . . 2n, 4a . . . 4n, and 6a . . . 6n are connected at one end to the terminal 16 which is grounded. The variable resistors 7a . . . 9n are connected through their sliders to channel selection switches 10a . . . 12n which in turn are connected to a band selection switch 13. The movable contact of the band selection switch 13 is connected to the output terminal 14.
To tune in a desired channel, the band selection switch 13 is changed over to the band containing the resistor that produces the tuning voltage corresponding to the desired channel and at the same time one of the channel selection switches 10a . . . 12n which corresponds to the desired channel is closed. This supplies the tuning voltage to the electronic tuner through the terminal 14, thereby tuning in the desired channel. The channel selection switches 10a, 11a, 12a are linked with the corresponding channel selection switches 10b, 11b, 12b, . . . , and 10n, 11n, 12n so that each group of corresponding switches move simultaneously.
Since it is necessary to provide a channel selection switch for each variable resistor, the conventional device is complex in construction and large in size and requires a large number of component parts pushing up the production cost.